Howard
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« on: 22.09. 2011 16:18 » |
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I brought my `51 A7 as a basket case. I am now at a stage where I need to do something about the carb. The original 276 carb has stripped treads and is generally worn out. A new one is about £300, however a new Concentric carb is a little over a £100.Apart from the look not being original, is there anything wrong with putting a concentric carb on ??
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900triple
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« Reply #1 on: 22.09. 2011 17:59 » |
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I believe that a lower cost alternative is a Mikuni from a Yamaha RD250 or LC 250....cost from zero if a mates got one to £15 from an autojumble. And probably a better performing carb anyway...
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muskrat
Forum Oracle
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Lake Conjola NSW Oz
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« Reply #2 on: 22.09. 2011 22:27 » |
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G'day Howard,
got one on my '51 A7. It has a '57 SS top end with A10 valves and 32mm Mk1 concentric. A 26 or 28mm will work for you. It will not work on an A10 plunger as it sits higher and fouls the frame.
Cheers
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Only young once, immature forever. Now how can I make this go faster. '51 A7 plunger, '57 A7SS now A10, '71 A65 Lightning (gone to god) '76 XT500, '83 CB1100F, next project a '64 A65.  |
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Pete Gray
A's best friend
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« Reply #3 on: 23.09. 2011 12:32 » |
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Had one on my 61 A7 for many years, no problems.
Not sure what diameter it is though.
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Pete
1961 Swinging arm A7
2000 BMW R1100R
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manormike
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Fareham, UK, 1960 A10
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« Reply #4 on: 23.09. 2011 16:33 » |
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Howard
If second hand is allowable to reduce cost then I would say a concentric is a pretty good bet. Yes the Japanese carbs are technically better but the Amal is readily available in numbers at jumbles etc, and jets etc can be ordered from Burlen if need be. There are a few things to look out for, noted on this forum and some others, but plenty of experience around if when you need it. I have a 28 mm concentric on the A10 and it starts easily, idles well and runs really sweet and economically.
Cheers
Mike
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Howard
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« Reply #5 on: 23.09. 2011 19:07 » |
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Thanks Guys....regards Howard
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iansoady
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« Reply #6 on: 24.09. 2011 13:19 » |
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Howard
If second hand is allowable to reduce cost then I would say a concentric is a pretty good bet.
Mind you they wear out quickly so need a good checking over - especially the fit of the slide and the flatness of the mounting flange. Otherwise they are as Mike says easy to tune and get bits for. |
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Ian. 1962 Golden Flash (arrived) 1955 Velo Viper/Venom (departed) 2004 Triumph Tiger 955i (staying)  |
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ebsbury
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57 A7SS
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« Reply #7 on: 24.09. 2011 20:06 » |
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You can get hard anodised alloy slides from Amal that reduce the wear - in fact the slide will probably out live the carb.
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manormike
A's best friend
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Fareham, UK, 1960 A10
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« Reply #8 on: 25.09. 2011 12:50 » |
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Much better wear characteristics with different material for slide and body. Mine has a chromed brass (plain brass would have been better IMO) slide which is a really nice fit in the well used body. But its dimensions from needle clip to base and cutaway were far from accurate compared with standard to begin with. Cost about £30 to add to budget.
Another frequent issue is blocking of the pilot bush, but I think the new ones have reverted to pilot jet under the body. At our Hants camp this August a guy showed a modified pilot air screw which incorporated the pilot jet, so it is ideally positioned yet easily cleaned. He is working with Burlen (Amal owners) on this. Generally available soon?
Float fuel level can be quite critical in my experience. A small adjustment, lowering of level made a big difference to mixture and fuel consumption.
Perhaps the concentric is not so good after all, but it can be made to work very well.
Cheers
Mike
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ebsbury
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57 A7SS
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« Reply #9 on: 25.09. 2011 16:46 » |
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Amal are selling the new carburetters as "Premier" Carbs" They come with anodised slides, stayup floats and the new pilot jet. The jet replaces the bush and looks like a cross between a pilot air screw and a monobloc pilot jet. It screws into the carburetter in opposite side of the carb to the pilot air screw so the jet is in the best position for four stroke engines (which is why the bush is used for 4 strokes) but adjusting the idle stays the same. There was a thread about them on the Britbike forum: http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=384863&Searchpage=8&Main=42709&Words=+amal&Search=true#Post384679 |
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manormike
A's best friend
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Fareham, UK, 1960 A10
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« Reply #10 on: 25.09. 2011 21:52 » |
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Thanks for that link ebsbury. Interesting.
Hadn't realised the pilot jet improvement is not retrofittable, shame.
Cheers, Mike
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rocker21
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« Reply #11 on: 06.10. 2011 14:48 » |
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there is an alternative carb available from JRC engineering in the states and it is a low cost item and they are very helpful, the throttle slide is hard chrome plated and it works very well, i have fitted one to my A7ss, it is a modern carb for modern fuels. the bike runs a lot better and it bolts on where the old amal carb was. I am very pleased with it, not for those who want everything original but if you want to ride then it is the way to go.
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